The present invention relates to a side airbag apparatus that protects an occupant seated in a vehicle seat from an impact by inflating an airbag outside and inside the vehicle seat when the impact is applied to the seat from a side, for example, due to a side collision.
Side airbag apparatuses are widely known as apparatuses that protect an occupant seated in a vehicle seat when an impact is applied to the seat from a side, for example, due to a side collision. A typical side airbag apparatus includes an inflator and an airbag, which is inflated with inflation gas supplied from the inflator. The inflator and the airbag are installed in the outer side of the seat back (backrest) of a vehicle seat.
One known form of the side airbag apparatus includes an airbag having a main inflation portion (a main airbag) and an auxiliary inflation portion (an auxiliary airbag) as disclosed in, for example, Japanese Laid-Open Patent Publication No. 2009-23494. The main inflation portion and the auxiliary inflation portion are accommodated in the outer side portion of the seat back. The words inside the parentheses following the names of the components are the names of the components used in Japanese Laid-Open Patent Publication No. 2009-23494.
The main inflation portion is inflated by inflation gas supplied from the inflator and projects from the seat back to be deployed forward between the occupant and the side wall of the vehicle. Prior to the deployment of the main inflation portion outside the seat back, the auxiliary inflation portion is inflated inside the seat back by inflation gas to push the occupant inward. The inflated auxiliary inflation portion pushes a part of the seat back that is forward of the auxiliary inflation portion, so that the part bulges diagonally forward and inward. The bulging part pushes the back of the occupant leaning against the seat back, thereby moving the occupant inward. This enlarges the space between the occupant and the side wall, thereby facilitating forward deployment and inflation of the main inflation portion.
If, for example, employed in a vehicle seat as disclosed in Japanese Laid-Open Patent Publication No. 2011-105126, the above-described airbag apparatus has the following drawbacks.
The vehicle seat disclosed in Japanese Laid-Open Patent Publication No. 2011-105126 includes a seat frame, which constitutes the framework of the seat back. The seat frame includes a pressure receiving plate (a plastic plate), which is arranged at the center in the vehicle width direction, and an outer frame portion, which is separated from and surrounds the pressure receiving plate. The pressure receiving plate is used to stably support the back of the occupant seated in the vehicle seat and is arranged at the rear end of the seat back. Part of the outer frame portion that is located in the outer side portion of the seat back is constituted by an outer side frame portion. The words inside the parentheses following the names of the components are the names of the components used in Japanese Laid-Open Patent Publication No. 2011-105126.
If the above-described airbag apparatus is employed in the vehicle seat of the publication, the airbag and the inflator, which form the main part of the side airbag apparatus, are installed in the outer side portion of the seat back. The auxiliary inflating portion is accommodated in part of the outer side portion of the seat back that is forward of the pressure receiving plate. When the inflator discharges inflation gas, the main inflation portion and the auxiliary inflation portion are respectively inflated. At this time, the auxiliary inflation portion is pushed from the front by the occupant and inflated rearward and may enter the gap between the outer side frame portion and the pressure receiving plate. This reduces the reaction force of the auxiliary inflation portion that acts to push the part of the seat back forward of the auxiliary inflation portion and cause the part to bulge inward and diagonally forward. As a result, the movement of the occupant inward and the enlargement of the space between the occupant and the side wall may be insufficient.